This site recommends using Plex to transcode unsupported codecs for the Raspberry Pi's consumption (Raspbmc in my case) via Plex Media Centre on the HTPC and the PleXBMC add-on on the Pi.
Could this be used to improve performance, i.e. would using the transcoding to down-convert resolution improve the Pi's playback performance? We use our's with a Wifi connection, so would the same reduce bandwidth usage and hence buffering?
It seems like it would to me, but I'm not familiar enough with transcoding, Raspbmc nor the Pi's set-up to conclusively answer this.